The use of field-deployed medical devices, such as portable defibrillators, is achieving widespread acceptance. Such devices are designed to be used in high-stress environments by people who may not be well trained. Thus, the medical devices commonly provide audible cues to the user to guide the use of the medical device. However, such medical devices may be deployed in greatly disparate noise environments ranging from very quiet, such as an office setting, to very loud, such as a railroad station. Thus, the audible cues must compete with drastically different ambient sounds that interfere with the intelligibility of the audible cues. Portable devices are also constrained by size, weight, and power limitations.